Historically push-pull D.C. to A.C. power converters have been plagued with crossover problems when both bipolar switching transistors are on during a half cycle. Field effect transistors have contributed substantially to the elimination of this problem, but it may still occur when the secondary of the power transformer is heavily loaded with capacitance or the interwinding capacitance is substantial. In these cases, the level of the switching current during turn-on becomes much higher than the level of the current during the remainder of the cycle.
The switching current is controlled, or minimized, in the present invention by the insertion of a choke winding in the center tap of the transformer. Energy stored in the choke winding prevents excessive voltage from appearing across the switches during the turn-off portions of the cycle. In addition, the leakage inductance energy of the primary of the transformer is returned to a storage capacitor to raise the efficiency of the converter.